Under Armour lost about $600 million in value after retailer Foot Locker said sales of Steph Curry's new shoe were softer than expected. Foot Locker CEO Dick Johnson said (via ESPN.com ) the Curry 3 "started off a bit slower than the previous models," causing a sell-off in the stock market.

While the price of the shoe has increased from the Curry 2 and 2.5 shoes to $140, Johnson remains confident in Under Armour as a company. "We're optimistic that they [Under Armour] are going to be able to continue to keep that [footwear business] with some momentum behind it and certainly expand their footwear offerings," Johnson said.

Curry, who wears a high-ankle version of the shoe during games but an everyday pair during warm-ups, is Under Armour's most prominent endorser although his products make up only about 5 percent ($200 million) of its annual business.

Still, this has been a bizarre dip for UA endorsers across the board. In the NFL, Cam Newton was MVP like Curry in 2015 but has had a rough 2016 that started with losing in the Super Bowl. Bryce Harper's dropoff from an NL MVP season was similarly stunning. Tom Brady, Jordan Spieth and Lindsey Vonn also are signed to Under Armour.